Continued growth in the electronics and computer industries, and indeed in the economy in general, is increasingly driven by the demand for access to the Internet and the myriad of services and features that it provides. The proliferation in the use of portable computing equipment, such as laptop computers, hand-held Personal Digital Assistants (PDAs) and Internet-enabled cellular telephones have resulted in a corresponding increase in demand for wireless access to computer networks. However, at the present time, existing wireless networks, such as the cellular telephone network, are not optimum for data communications. This is at least in part due to the architecture of such networks as originally designed. In particular, these networks were intended to support voice communications, as compared to the digital communication protocols needed for Internet packet-oriented communications. For example, voice grade services typically require access to a communication channel bandwidth of approximately 3 kilohertz (kHz). While techniques do exist for communicating data over such radio channels at a rate of 9.6 kilobits per second (kbps), such low bandwidth channels do not lend themselves directly to efficient transmission of data at the typical rates of 56.6 kbps or higher that are now commonly expected using wireless modems.
In addition, the very nature of Internet traffic itself is different from the nature of voice traffic. Voice communication requires a continuous duplex connection, that is, a user at one end of a connection expects to be able to transmit and receive to a user at the other end of a connection, while at the same time the user at the other end is also transmitting and receiving.
However, the usage patterns of Internet data transmission systems are quite different from voice. For example, consider that access to Web pages over the Internet in general is burst-oriented. Typically, the user of a remote client computer first specifies the address of a Web page to a browser program. The browser program at the client computer then sends the request as a Transmission Control Protocol (TCP)/Internet Protocol (IP) message packet, which is typically about 100 bytes in length, to a network Web server. The Web server then responds with the content of the requested Web page, which may include anywhere from approximately 10 kilobytes to several megabytes of text, image, audio or video data. The user may thereafter spend several seconds or even several minutes reading the contents of the page before specifying a next Web page to be downloaded.
The result is that a typical Internet connection remains idle for a relatively long period of time. However, once a request is made, the user expects the information to be transmitted to the client at a relatively rapid rate. Therefore, making available channels only on an instantaneous “as needed” basis makes sense and indeed is a requirement if wireless data transfer services are to efficiently co-exist with the existing wireless voice communication systems. Therefore, dynamic traffic channel allocation schemes are required to increase the efficiency of high performance wireless data communication systems in an effort to more efficiently utilize available channel resources.
Furthermore, in most wireless systems, there are typically many more potential users or subscribers than available radio channel resources. Therefore, some type of demand-based multiple access technique is therefore typically required to make maximum use of the available radio channels. Multiple access is often provided in the physical layer, such as by Frequency Division Multiple Access (FDMA) or by schemes that manipulate the radio frequency signal such as Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA). In any event, the nature of the radio spectrum is such that it is a medium that is expected to be shared. This is quite dissimilar to the traditional environment for data transmission, in which a wired medium such as a telephone line or network cabling is relatively inexpensive to obtain and to keep open all the time.